1. Field of the Invention
The present invention relates to a control equipment for an electric vehicle and control method thereof, more particularly to the control equipment and control method suitable to suppress the vibration of an electric vehicle.
2. Description of the Prior Art
Generally, a plurality of elastic members such as elastic shafts and couplings are used to transmit the torque from a motor to an electric vehicle. Thus, the electric vehicle forms an elastic system as a whole. As a result, the mechanical vibration of the electric vehicle may occur when the motor torque changes suddenly. The mechanical vibration makes the driver uncomfortable.
In order to solve the above problem, for example, Japanese Patent Application Laid-open No. 4-145806 (1993) discloses an electric vehicle provided with a torque control equipment for controlling a motor current so as to suppress such the vibration, in which the torque control equipment includes vibration detecting means for detecting the vibration of the electric vehicle.
In the construction described above, the vibration of the electric vehicle is detected, and the current supplied to the motor can be increased or decreased when the vibration of the electric vehicle occurred. As a result, the vibration of the electric vehicle can be suppressed and the uncomfortable condition during driving can be avoid.
However, in the conventional vibration suppression technique, if the components of vibration enter the motor speed owing to the mechanical resonance vibration of the electric vehicle generated when the motor torque is changed suddenly, for example, by the quick acceleration, the stable control operation may be disturbed. This mechanical vibration of the electric vehicle may occur when the electric vehicle is accelerated from the initial speed of the medium speed, for example, when accelerated from 80 km/h to 100 km/h.